Combustion chambers in the piston head for compression ignition engines with direct fuel injection are known. They are formed by a rotary side wall passing into a shaped bottom of the combustion chamber. The combustion chamber axis is identical to the cylinder axis or lies in its close vicinity. The injection jet is placed in the middle or near the middle of the cylinder head between intake and exhaust channels. Such centrally located combustion chambers, whose injection jet is also centrally located, are capable of creating an optimum filling whirl in the combustion chamber, optimum fuel mixture and its distribution in the combustion chamber, i.e. a rich mixture at the combustion chamber walls and a leaner mixture in the middle of the combustion chamber. The process of combustion is thus enhanced and there is an increase in combustion pressures ensuing from this. Fuel consumption and exhaust emissions are improved as well.
Rotary combustion chambers for compression ignition engines with direct fuel injection by multiport jet are also known. DE 30 18 577 discloses a combustion chamber misaligned in the piston bottom and equipped in the middle part of the combustion chamber bottom with a rotary lug which together with a further shaping of the combustion chamber serves for optimizing fuel mixture whirl. With respect to the reduction of volume of the central part of the combustion chamber where the leanest fuel mixture is after the injection, a faster combustion of the fuel mixture occurs, which unfavorably influences the speed of increase in combustion pressures.
All known combustion chambers that are capable of providing optimum whirling of fuel filling, the suitable distribution of fuel mixture, and the optimum increase in the combustion pressure are arranged co-axially with the cylinder axis or misaligned by a maximum of 0.2 times the combustion chamber diameter. If the misalignment of the combustion chamber is larger, during the air filling compression the whirl splits and more whirls are created and this unfavorably influences the composition and distribution of the fuel mixture in the combustion chamber which affects ignition, combustion pressures, fuel consumption and harmful emissions.
Yet, a larger misalignment of the combustion chamber is desirable with respect to the requirement of a larger misalignment of the injection jet which enables an uncompromising location of the intake and exhaust channel in the engine cylinder head and valve gear.